Presented up front is the final product for which the rest of this document describes. It is a map of the ORMGP jurisdiction discretized into ~10km² sub-watersheds. Clicking at any sub-watershed will return a number of properties. In the figure below, sub-watersheds are colour-coded according to their degree of impervious cover. # {r, echo=FALSE, message=FALSE, warning=FALSE, out.height='600px', out.width='100%', fig.cap="ORMGP v.2020 10km² sub-watershed map. Click a subwatershed to view spatial properties."} # library(leaflet) # library(rgdal) # ormgp <- readOGR("shp/owrc20-50a_SWS10-final.geojson",verbose = FALSE) # # leaflet(ormgp) %>% # addProviderTiles( providers$Stamen.TonerLite, options = providerTileOptions(noWrap = TRUE) ) %>% # addPolygons(color = ~colorQuantile("YlGnBu", ormgp$perimp)(perimp), # popup = ~paste0('<b>sub-watershed: ',mmID,'</b>', # '<br> area: ',round(Area/1000000,1),'km²', # '<br> permeability: ',perm, # '<br> impervious cover: ',round(perimp*100,0),'%', # '<br> canopy cover: ',round(percov*100,0),'%', # '<br> open water cover: ',round(perow*100,0),'%', # '<br> wetland cover: ',round(perwl*100,0),'%' # ) # ) # #
The 3 million hectare ORMGP jurisdiction is subdivided to a number of 10km² sub-watersheds as a basis for hydrometeorological data analysis. Every sub-watershed has a defined topological order in which headwater sub-watersheds can easily be mapped to subsequent downstream sub-watersheds, and so on until feeding the great lakes. The intent here is to deem these sub-watersheds a “logical unit” for climatological and water budget analyses. Below is a description of the derivation the v.2020 OWRC 10km² sub-watershed map and its derivatives including:
Below first describes the processing of a Provincial Digital Elevation Model (DEM) yielding a “hydrologically-correct” model of the ORMGP ground surface. From this information, the ORMGP region is portioned into 2,813 ~10km² sub-watersheds.
Next, the hydrologically-corrected digital elevation model (HDEM) is further process to derive a number of metrics aggregated at the sub-watershed scale.
Ground surface elevations were collected from the 2006 version of the Provincial (Ministry of Natural Resources) Digital Elevation Model (DEM). This is a 10x10m² DEM derived from 1:10,000 scale OBM base mapping based on photogrammetic elevation points and 5m contours where the photogrammetic elevation points did not exist. An up-scaled 50x50m² Digital Elevation Model (DEM) is produced by merging the tiles shown below:
MNR 2006 Provincial DEM tiles shown in green.
Elevation data were up-scaled by taking the average of known elevations occurring within every 50x50m² cell. The resulting grid is a 5000x5000 50m-uniform cell grid, with an upper-left-corner origin at (E: 545,000, N: 5,035,000) NAD83 UTM zone 17.
An automated topological topological analysis is performed on the DEM using the following methodologies:
Cell slopes and aspects are computed using a 9-point planar regression from the cell’s elevation plus it’s 8 neighbouring elevations.
While automated hydrological correction is quite powerful when applied to the Provincial DEM, there are in rare places where the algorithm fails to capture mapped flow paths (usually in flatter rural regions close to embanked roads). Fortunately, these errors can be easily corrected by imposing flow directions using hand-drawn flow paths. Flow paths are save as polylines, where its vertices are ordered according to flow direction.
With the current version (v.2020), 10 flow corrections have been imposed and are saved in a set of shapefiles. There is at the moment 1 new flow path correction in queue and will be imposed for the next release. This is to say that this layer and its derivatives are continually being updated.
{#fig.hdem}
The benefit of computing the flow direction topology associated with the HDEM is that any user a could place a “virual particle” on the landscape and follow its drainage path as it traverses toward its terminous; in this case, the Great Lakes.
More importantly however, given an HDEM, one can also efficiently compute the contributing area to any selected point on the landscape. (A live demonstration of this is presented below.) This feature provides the means to validate the procesessing presented in this document.
Locations of 96 current and historical stream flow gauges are used to compare drainage areas reported to the drainage areas computed using the HDEM. Sources of the station locations were collected from the Water Survey of Canada and the Toronto Region Conservation Authority. The table below lists the stations used, followed by a figure comparing their match to the HDEM. As mentionned earlier, this layer will continually be updated with input from users and it is expected that this validation can only improve.
| Station ID | Long | Lat | reported (km²) | computed (km²) | difference (%) |
|---|---|---|---|---|---|
| 02EC008 | -79.3 | 44.3 | 272.0 | 297.9 | 9.5 |
| 02EC009 | -79.5 | 44.1 | 176.0 | 176.8 | 0.4 |
| 02EC010 | -79.7 | 44.0 | 51.3 | 44.0 | -14.3 |
| 02EC011 | -79.1 | 44.4 | 291.0 | 292.4 | 0.5 |
| 02EC018 | -79.2 | 44.3 | 347.0 | 336.2 | -3.1 |
| 02ED007 | -79.6 | 44.7 | 168.0 | 183.5 | 9.2 |
| 02ED013 | -79.9 | 44.6 | 121.0 | 121.3 | 0.2 |
| 02ED014 | -80.0 | 44.2 | 190.0 | 181.4 | -4.5 |
| 02ED015 | -80.1 | 44.3 | 244.0 | 253.4 | 3.9 |
| 02ED017 | -79.8 | 44.7 | 65.2 | 58.5 | -10.3 |
| 02ED024 | -79.6 | 44.8 | 244.0 | 243.2 | -0.3 |
| 02ED026 | -80.0 | 44.0 | 176.0 | 177.2 | 0.7 |
| 02ED029 | -79.8 | 44.1 | 479.0 | 479.8 | 0.2 |
| 02ED100 | -79.8 | 44.0 | 86.0 | 75.0 | -12.8 |
| 02ED101 | -79.9 | 44.1 | 328.0 | 328.9 | 0.3 |
| 02ED102 | -79.9 | 44.2 | 216.0 | 218.9 | 1.4 |
| 02GA014 | -80.3 | 43.9 | 663.0 | 597.3 | -9.9 |
| 02GA015 | -80.3 | 43.5 | 567.9 | 573.2 | 0.9 |
| 02GA016 | -80.3 | 43.7 | 784.8 | 719.6 | -8.3 |
| 02GA029 | -80.2 | 43.5 | 231.0 | 242.5 | 5.0 |
| 02GA031 | -80.1 | 43.6 | 41.5 | 44.1 | 6.4 |
| 02GA040 | -80.3 | 43.6 | 167.0 | 170.1 | 1.8 |
| 02GA041 | -80.4 | 44.1 | 66.5 | 66.3 | -0.3 |
| 02HB001 | -80.0 | 43.8 | 208.8 | 202.5 | -3.0 |
| 02HB004 | -79.8 | 43.5 | 193.0 | 194.9 | 1.0 |
| 02HB005 | -79.9 | 43.5 | 101.3 | 105.0 | 3.6 |
| 02HB008 | -79.9 | 43.6 | 131.0 | 127.4 | -2.7 |
| 02HB011 | -79.9 | 43.4 | 242.0 | 243.0 | 0.4 |
| 02HB013 | -80.1 | 43.9 | 60.6 | 59.9 | -1.2 |
| 02HB015 | -80.1 | 43.4 | 63.5 | 54.2 | -14.6 |
| 02HB018 | -79.9 | 43.8 | 414.7 | 409.3 | -1.3 |
| 02HB020 | -80.1 | 43.8 | 32.3 | 32.9 | 1.9 |
| 02HB022 | -80.0 | 43.4 | 123.4 | 117.7 | -4.6 |
| 02HB024 | -80.0 | 43.6 | 18.9 | 20.2 | 6.8 |
| 02HB025 | -79.9 | 43.6 | 644.8 | 639.6 | -0.8 |
| 02HB027 | -79.7 | 43.4 | 24.5 | 25.8 | 5.4 |
| 02HC003 | -79.5 | 43.7 | 802.0 | 805.6 | 0.4 |
| 02HC005 | -79.4 | 43.7 | 88.1 | 89.2 | 1.2 |
| 02HC009 | -79.6 | 43.8 | 190.9 | 189.8 | -0.6 |
| 02HC013 | -79.2 | 43.8 | 89.1 | 89.0 | -0.1 |
| 02HC017 | -79.8 | 43.7 | 68.6 | 62.7 | -8.6 |
| 02HC018 | -79.0 | 43.9 | 100.3 | 99.8 | -0.5 |
| 02HC019 | -79.1 | 43.9 | 93.5 | 86.9 | -7.0 |
| 02HC022 | -79.2 | 43.9 | 181.3 | 178.9 | -1.3 |
| 02HC023 | -79.7 | 43.9 | 62.2 | 63.4 | 1.9 |
| 02HC024 | -79.4 | 43.7 | 318.5 | 322.6 | 1.3 |
| 02HC025 | -79.6 | 43.8 | 296.3 | 300.0 | 1.2 |
| 02HC027 | -79.5 | 43.7 | 58.0 | 65.9 | 13.6 |
| 02HC028 | -79.2 | 43.9 | 83.6 | 62.4 | -25.3 |
| 02HC030 | -79.6 | 43.6 | 205.0 | 181.1 | -11.6 |
| 02HC031 | -79.7 | 43.8 | 142.2 | 141.0 | -0.9 |
| 02HC032 | -79.6 | 43.9 | 94.8 | 91.9 | -3.1 |
| 02HC033 | -79.5 | 43.6 | 67.8 | 67.9 | 0.2 |
| 02HC038 | -79.2 | 43.9 | 52.0 | 62.4 | 20.1 |
| 02HC047 | -79.8 | 43.9 | 163.5 | 167.6 | 2.5 |
| 02HC049 | -79.1 | 43.8 | 257.5 | 257.1 | -0.2 |
| 02HC051 | -79.8 | 43.9 | 42.0 | 41.1 | -2.1 |
| 02HC053 | -79.3 | 43.9 | 59.0 | 59.3 | 0.5 |
| 02HC054 | -79.0 | 44.0 | 39.0 | 38.9 | -0.3 |
| 02HC055 | -79.0 | 43.9 | 37.6 | 37.6 | -0.1 |
| 02HD003 | -78.4 | 44.0 | 67.3 | 72.9 | 8.3 |
| 02HD004 | -78.4 | 44.0 | 46.1 | 40.1 | -13.1 |
| 02HD006 | -78.7 | 43.9 | 80.9 | 78.4 | -3.2 |
| 02HD008 | -78.9 | 43.9 | 95.8 | 95.8 | 0.0 |
| 02HD009 | -78.6 | 43.9 | 80.7 | 81.0 | 0.3 |
| 02HD010 | -78.0 | 44.0 | 63.8 | 63.4 | -0.6 |
| 02HD012 | -78.3 | 44.0 | 241.9 | 239.9 | -0.8 |
| 02HD013 | -78.8 | 43.9 | 42.9 | 42.9 | 0.2 |
| 02HD018 | -77.7 | 44.1 | 16.8 | 16.3 | -2.9 |
| 02HD019 | -78.2 | 44.0 | 122.1 | 122.7 | 0.5 |
| 02HG002 | -79.0 | 44.1 | 32.6 | 41.4 | 26.8 |
| 02HJ001 | -78.3 | 44.3 | 116.2 | 116.2 | 0.1 |
| 02HJ003 | -78.0 | 44.3 | 282.6 | 281.6 | -0.4 |
| 02HJ005 | -78.4 | 44.1 | 11.6 | 11.6 | 0.1 |
| 02HK005 | -77.9 | 44.8 | 456.0 | 440.5 | -3.4 |
| 02HK006 | -77.7 | 44.5 | 552.8 | 528.9 | -4.3 |
| 02HK007 | -77.8 | 44.1 | 160.5 | 160.8 | 0.2 |
| 02HK008 | -77.5 | 44.3 | 93.0 | 90.4 | -2.8 |
| 02HK009 | -77.9 | 44.2 | 82.6 | 79.7 | -3.5 |
| 02HK011 | -77.6 | 44.1 | 33.0 | 32.7 | -1.0 |
| 02HL003 | -77.4 | 44.5 | 429.0 | 424.8 | -1.0 |
| 02HL005 | -77.6 | 44.5 | 296.9 | 294.6 | -0.8 |
| 02KD002 | -77.8 | 45.1 | 844.5 | 789.4 | -6.5 |
| HY010 | -79.1 | 43.9 | 15.1 | 15.1 | 0.0 |
| HY023 | -79.1 | 43.9 | 62.1 | 62.1 | 0.0 |
| HY024 | -79.7 | 43.7 | 81.5 | 81.5 | 0.0 |
| HY028 | -79.1 | 43.9 | 11.3 | 11.3 | 0.0 |
| HY034 | -79.2 | 43.8 | 11.8 | 11.8 | 0.0 |
| HY040 | -79.1 | 43.8 | 2.7 | 2.7 | 0.0 |
| HY045 | -79.6 | 43.7 | 38.4 | 38.4 | 0.0 |
| HY047 | -79.1 | 44.0 | 23.1 | 23.1 | 0.0 |
| HY051 | -79.1 | 43.8 | 25.7 | 25.7 | 0.0 |
| HY052 | -79.1 | 43.8 | 8.0 | 8.0 | 0.0 |
| HY059 | -79.7 | 43.7 | 36.9 | 36.9 | 0.0 |
| HY065 | -79.1 | 43.9 | 13.7 | 13.7 | 0.0 |
| HY082 | -79.2 | 43.9 | 34.4 | 34.4 | 0.0 |
An overlay analysis is the process of overlaying 2 or more spatial layers and capturing statistics associated with their relative coverage. In this case, the sub-watershed layer is overlain by Provincial land-use and surficial geology layers to obtain information like percent impervious, relative permeability, etc.
Provincial layers discussed in more detail below have in all cases been re-sampled to the 50x50m² grid associated with the hydrologically corrected DEM. It is from these rasters where the aggregation of watershed characteristics is computed.
The Ministry of Natural Resources and Forestry (2019) SOLRIS version 3.0 provincial land use layer is employed to aggregate imperviousness and canopy coverage at the sub-watershed scale. In areas to the north, where the SOLRIS coverage discontinues, interpretation was applied by:
The dominant SOLRIS land use class (by area) is assigned the Land use class index for every 50x50m² grid cell.
For any ~10km² sub-watershed and give a 50x50m² grid , there should be a set of roughly 4,000 SOLRIS land use class indices. Using a look-up system, the set of cells contained within a sub-watershed are assigned a value of imperviousness, water body, wetland and canopy coverage (according to their SOLRIS index) and accumulated to a sub-watershed sum.
| Index | Name | Imperviousness (%) | Canopy cover (%) |
|---|---|---|---|
| 11 | Open Beach/Bar | ||
| 21 | Open Sand Dune | ||
| 23 | Treed Sand Dune | 50 | |
| 41 | Open Cliff and Talus | ||
| 43 | Treed Cliff and Talus | 50 | |
| 51 | Open Alvar | ||
| 52 | Shrub Alvar | 25 | |
| 53 | Treed Alvar | 50 | |
| 64 | Open Bedrock | ||
| 65 | Sparse Treed | 40 | |
| 81 | Open Tallgrass Prairie | 10 | |
| 82 | Tallgrass Savannah | 35 | |
| 83 | Tallgrass Woodland | 85 | |
| 90 | Forest | 100 | |
| 91 | Coniferous Forest | 100 | |
| 92 | Mixed Forest | 100 | |
| 93 | Deciduous Forest | 100 | |
| 131 | Treed Swamp | 50 | |
| 135 | Thicket Swamp | 50 | |
| 140 | Fen | 25 | |
| 150 | Bog | 25 | |
| 160 | Marsh | 25 | |
| 170 | Open Water | ||
| 191 | Plantations – Tree Cultivated | 85 | |
| 192 | Hedge Rows | 85 | |
| 193 | Tilled | ||
| 201 | Transportation | 85 | |
| 202 | Built-Up Area– Pervious | 10 | 10 |
| 203 | Built-Up Area– Impervious | 90 | |
| 204 | Extraction–Aggregate | ||
| 205 | Extraction –Peat/Topsoil | 10 | |
| 250 | Undifferentiated |